Since ancient times, the great demon prison Zzyzx has protected the world from the most dangerous servants of darkness, including Gorgrog, the Demon King. After centuries of plotting, the Sphinx is on the verge of recovering the five artifacts necessary to open the legendary prison. To thwart the Sphinx's designs and find a safe home for the five artifacts, Kendra, Seth, and the Knights of the Dawn must venture far beyond the walls of Fablehaven in a desperate struggle to control the keys to the demon prison.